106 



FOSSIL OOLITIC ASTERIAD^. 



shape, and become narrower as they approach the buccal regions of the ventral disc. Their 

 crests, or elevated portions, bear combs of long, slender, acicnlar spines, with bulbous bases ; 

 of these spines there are from four to six in each transverse row, (fig. 1 c) shows these 

 quadrate spiniferous ossicula with their crests of comb-like spines magnified. 



The arrangement of the dorsal surface of the rays is too obscure in the few portions of 

 those organs that are reversed to enable one to make out their details with certainty ; but 

 I think I can perceive pretty clearly the paxillated character of the spines, and that these 

 bodies, forming the radiated or brush-like crowns of the paxilla above described, are much 

 shorter and stouter than the marginal spines. 



Affinities and differences. — This fossil Starfish is quite unique ; the organic characters of 

 the skeleton so closely resemble those possessed by Solaster papposa, prepared expressly 

 for the purpose of minute comparison, that I cannot doubt its being a true Solaster, the 

 modifications in the form of the bones of the rays and in the number of these processes 

 clearly prove, however, that it appertains to an extinct species, in which all the generic 

 characters of the group are well preserved. 



Locality and Btratigrapldcal position. — This Star-fish was discovered by the workmen 

 at Windrush Quarry, Gloucestershire, in a block of oolitic freestone, belonging to the Great 

 Oolite. It is now the property of the Earl of Ducie ; the species was dedicated to his lordship 

 by Professor Forbes, who first described it in the fifth decade of " British Organic Remains," 

 published by the ' Geological Survey of Great Britain.'^ 



Gerius—^OmhSr^m^, Agassiz. 



This genus, as established by Agassiz^ in his Prodrome, includes Star-fishes with a 

 pentagonal body, having the margin bordered with a pair of large plates, which sometimes 

 carry spines ; the upper surface of the body is covered with small tetragonal, or polygonal 

 ossicles fitted within the marginal framework, the suckers are biserial, and the vent opens 

 near the centre of the dorsal surface. 



Miiller and TroscheP suppressed the genus Goniaster, and formed, instead, three genera, 

 Astrogonium, Goniodiscus, Stellaster, whose diagnostic characters were chiefly obtained 

 from the structure of the marginal plates, as the following definitions indicate. 



1. Astrogonium. — The large marginal plates are smooth towards the centre, and the 

 border is surrounded by a circle of granules. 



1 ' Memoirs of the Geol. Survey, British Organic Remains,' pi. v, p. 3. 



2 "Prodrome d'une Mouogr. des Radiaires Echinodermes," ' Memoires de la Societe des Sciences 

 Naturelles de Neuchatel,' tome i, p. 191. 



2 'System der Asteriden,' p. 52 — '62. 



